Programming Concepts
The Multimedia Java API is based around four main types of classes in the javax.microedition.media package—the Manager, the Player, the PlayerListener and various types of Control.
Java ME programmers wishing to use JSR 135 would first make use of the static methods of the Manager class. Although there are other methods such as playTone, the main method used is createPlayer. This takes either a URI or an InputStream, and a MIME type. In most cases, URIs are used. Common URI protocols used include:
- file:
- resource: (which may extract a file from within the JAR of the MIDlet, but is implementation-dependent)
- http:
- rtsp:
- capture: (used for recording audio or video)
The MIME type is optional, and is inferred from the data passed in if not supplied.
The createPlayer method returns an implementation of the Player interface (even if you use a capture: protocol URI). This has core methods that are applicable to all players, such as starting and stopping the media, and requesting that it loop. You can also setPlayerListener to an object implementing the PlayerListener interface, which will receive various events related to the clip (starting, stopping, media finishing, etc.)
Player classes also have a getControl method that returns an implementation of a particular Control. A Control handles any optional APIs which are not applicable to all media types. Any given Player may or may not be able to supply an implementation of any given Control.
(Typically, the Control returned is actually the Player itself, but this is not guaranteed to be the case.)
The set of controls implemented by a Player is not limited; however, some standard ones are defined in the javax.microedition.media.control package by the JSR:
| Control Interface | Description |
|---|---|
| FramePositioningControl | A control for video data that allows access to individual frames. |
| GUIControl | A control for data that requires a display, such as video. |
| MetaDataControl | Used to determine the metadata information stored within amedia stream, such as title, copyright, author, and so on. |
| MIDIControl | A fully functional control that enables access to a device’s MIDI player. |
| PitchControl | Used to control the pitch (frequency) of audio data. |
| RateControl | Used to control the playback rate of a Player. |
| RecordControl | Allows you to control the recording of data from a capture device, such as video from a camera or audio from a sound recorder. |
| StopTimeControl | A control that allows you to set a preset time when you want the Player to stop playing. |
| TempoControl | Similar to RateControl, this control allows you to change the tempo (speed) of playback for an audio Player, typically, a MIDI Player. |
| ToneControl | A fully functional control that allows you to play monotonic tone sequences. |
| VideoControl | Extends GUIControl and controls the display of video. |
| VolumeControl | The simplest control that allows you to control the volume of audio in a Player. |
(Others may be defined in JSR 234 (Advanced Multimedia Supplements).
A subset of JSR 135 is defined in JSR 118 (MIDP 2.0).
Read more about this topic: Java Mobile Media API
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